Lu Yahai, Murase Jun, Watanabe Akira, Sugimoto Atsuko, Kimura Makoto
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
FEMS Microbiol Ecol. 2004 May 1;48(2):179-86. doi: 10.1016/j.femsec.2004.01.004.
Photosynthesis by terrestrial vegetation is the driving force of carbon cycling between soil and the atmosphere. The soil microbiota, the decomposers of organic matter, is the second player carrying out carbon cycling. Numerous efforts have been made to quantify rhizodeposition and soil respiration to understand and predict the carbon cycling between the soil and atmosphere. However, there have been few attempts to link directly the soil microbial community to plant photosynthesis. We carried out a pulse-chase labeling experiment in a wetland rice system in which rice plants of various ages were labeled with (13)CO(2) for 6 h and the distribution of the assimilated (13)C to soil microorganisms was estimated by analyzing the (13)C profile of microbial phospholipid fatty acids (PLFAs). The results showed that total PLFA increased with plant growth, indicating an increase of microbial biomass. But the mono-unsaturated PLFAs increased faster than the branched chain fatty acids. The (13)C was incorporated into PLFAs immediately after the plant (13)CO(2) assimilation, proving the tight coupling of microbial activity to plant photosynthesis. In line with the finding of seasonal change in total PLFAs, more of (13)C was distributed to the straight chain fatty acids (16:0, 16:1omega7, 18:1omega7 and 18:1omega9) than to the branched chain fatty acids. The total plant carbon incorporation estimated from (13)C labeling roughly corresponded to the increase in total PLFAs over the growing season of plants. Our study suggests that microbial populations in rice soil differ greatly in their responses to plant photosynthate input.
陆地植被的光合作用是土壤与大气之间碳循环的驱动力。土壤微生物群作为有机物质的分解者，是进行碳循环的第二个参与者。为了理解和预测土壤与大气之间的碳循环，人们已经做出了许多努力来量化根系分泌物和土壤呼吸。然而，很少有人尝试将土壤微生物群落与植物光合作用直接联系起来。我们在一个湿地水稻系统中进行了一项脉冲追踪标记实验，用¹³CO₂对不同年龄的水稻植株标记6小时，并通过分析微生物磷脂脂肪酸（PLFA）的¹³C谱来估计同化的¹³C在土壤微生物中的分布。结果表明，总PLFA随着植物生长而增加，表明微生物生物量增加。但是单不饱和PLFA的增加速度比支链脂肪酸快。在植物同化¹³CO₂后，¹³C立即被纳入PLFA，证明了微生物活性与植物光合作用的紧密耦合。与总PLFA的季节变化结果一致，更多的¹³C分布在直链脂肪酸（16:0、16:1ω7、18:1ω7和18:1ω9）而不是支链脂肪酸中。根据¹³C标记估算的植物总碳同化量大致与植物生长季节总PLFA的增加量相对应。我们的研究表明，水稻土中的微生物种群对植物光合产物输入的反应差异很大。
